Display device with touch detection function, and electronic unit

ABSTRACT

A display device with a touch detection function including: a plurality of liquid crystal display elements performing display operation; a plurality of touch detection electrodes arranged side by side to extend in one direction, and each outputting a detection signal based on a change in an electrostatic capacitance caused by an external proximity object; a conductive film insulated from or connected with high resistance to the touch detection electrodes, and disposed to cover the touch detection electrodes; and a touch detection circuit detecting the external proximity object by sampling the detection signal. The conductive film has a sheet resistance equal to or smaller than a predetermined resistance value, and has a time constant larger than a predetermined minimum time constant defined by sampling timings in the touch detection circuit.

RELATED APPLICATION DATA

This application is a continuation of U.S. patent application No. Ser.13/227,019 filed Sep. 7, 2011, the entirety of which is incorporatedherein by reference to the extent permitted by law. The presentapplication claims the benefit of priority to Japanese PatentApplication No. JP 2010-205573 filed on Sep. 14, 2010 in the JapanPatent Office, the entirety of which is incorporated by reference hereinto the extent permitted by law.

BACKGROUND

This disclosure relates to a display device with a touch detectionfunction, and in particular, to a display device with a touch detectionfunction detecting touch events based on a change in an electrostaticcapacitance caused by an external proximity object, and an electronicunit including such a display device with a touch detection function.

In recent years, a display device capable of inputting information bymounting a contact detection device, which is a so-called touch panel,on a display device such as a liquid crystal display device, orintegrating the touch panel and the display device, and displayingvarious button images and the like on the display device instead oftypical mechanical buttons has attracted attention. The display deviceincluding such a touch panel does not require input devices such as akeyboard, a mouse, and a keypad, and therefore there is a tendency toexpand the use of such a display device to portable informationterminals such as mobile phones, in addition to computers.

As a method used in a touch detection device, some methods such asoptical method and a resistance method exist. However, an electrostaticcapacitance type touch detection device is promising which has arelatively simple configuration, is capable of detecting touch events atplural positions at a time, and is capable of achieving low powerconsumption which is considerable particularly for mobile terminals orthe like. For example, Japanese Unexamined Patent ApplicationPublication No. 2008-129708 (JP-A-2008-129708) discloses a touchdetection device including a plurality of X-direction electrodes and aplurality of Y-direction electrodes which is disposed to face theX-direction electrodes, and detecting touch events with use of a changeof an electrostatic capacitance caused by an external proximity object,the electrostatic capacitance being formed at each intersection betweenthe X-direction electrodes and the Y-direction electrodes. In addition,for example, in Japanese Unexamined Patent Application Publication No.2009-244958 (JP-A-2009-244958), a display device incorporating a touchdetection function, in which a common electrode for display originallyprovided in the display device is shared as one of a pair of electrodesfor a touch sensor, and the other of the pair of the electrodes (touchdetection electrode) is disposed to intersect with the common electrodehas been proposed.

Typically, measures against electro static discharge (ESD) are importantin electronic units. Static electricity is possibly applied to anelectronic unit, for example, in manufacturing the electronic unit andin its use by a user. For a touch detection device, some ESD protectionmeasures have been proposed. For example, in Japanese Unexamined PatentApplication Publication No. 2009-86077 (JP-A-2009-86077), a displaydevice mounted with a resistance film type touch detection device on aliquid crystal display panel has been described. In the display device,to eliminate static electricity generated at the time of bonding apolarizing plate in manufacturing process of the liquid crystal displaypanel, a transparent conductive film is formed on the liquid crystaldisplay panel so as to be in an electrically floating state, and afterthe polarizing plate is bonded, a jig is allowed to be in contact withthe transparent conductive film.

SUMMARY

However, in the above described JP-A-2008-129708 and JP-A-2009-244958relating to an electrostatic capacitance type touch detection devicehaving various advantages, ESD protection measures have not beendescribed at all. In the display device with a touch detection functiondescribed in JP-A-2008-129708 or JP-A-2009-244958, display is possiblydisturbed in response to application of static electricity by ESD.Particularly, display is possibly disturbed for a long time in a regionapart from an electrode for touch detection since static electricity isdifficult to be released. Moreover, like the display device with a touchdetection function described in JP-A-2008-129708, in a case where dummyelectrodes for improving optical characteristics are arranged in theregion, display is possibly disturbed for a further long time since thedummy electrodes are charged with static electricity.

In a display device described in JP-A-2009-86077, the transparentconductive film is in an electrically floating state. Therefore, forexample, in its use, in a case where a charged finger touches a touchpanel or other cases, there is a possibility that static electricity ischarged in the transparent conductive film and becomes difficult to bereleased from the transparent conductive film. In addition, inJP-A-2009-86077, provision of the transparent conductive film in a casewhere a resistance film type touch detection device is mounted isdescribed; however, a case of an electrostatic capacitance type touchdetection device is not described.

It is desirable to provide a display device with a touch detectionfunction and an electronic unit capable of reducing disturbance ofdisplay even in a case where static electricity is applied.

A display device with a touch detection function according to anembodiment of the disclosure includes a plurality of liquid crystaldisplay elements, a plurality of touch detection electrodes, aconductive film, and a touch detection circuit. The liquid crystaldisplay elements perform display operation. The plurality of touchdetection electrodes is arranged side by side to extend in onedirection, and each outputs a detection signal based on a change in anelectrostatic capacitance caused by an external proximity object. Theconductive film is insulated from or is connected with high resistanceto the touch detection electrodes, and is disposed to cover the touchdetection electrodes. The touch detection circuit detects the externalproximity object by sampling the detection signal. The conductive filmhas a sheet resistance equal to or smaller than a predeterminedresistance value, and a time constant larger than a predeterminedminimum time constant defined by sampling timings in the touch detectioncircuit.

An electronic unit according to an embodiment of the disclosure includesthe above-described display device with a touch detection function, andcorresponds to, for example, a television device, a digital camera, apersonal computer, a video camera, and a portable terminal device suchas a mobile phone.

In the display device with a touch detection function and the electronicunit according to the embodiments of the disclosure, when staticelectricity is applied, the sheet resistance of the conductive film isset to the predetermined resistance value or smaller in order to releasethe static electricity to the touch detection electrodes through theconductive film. In addition, to suppress reduction of touch detectionsensitivity due to provision of the conductive film, the time constantof the conductive film is set to be larger than the predeterminedminimum time constant.

In the display device with a touch detection function according to theembodiment of the disclosure, for example, the predetermined resistancevalue is desirably 10¹² Ω/sq. Moreover, for example, the touch detectioncircuit may detect the external proximity object based on a differencebetween a sampling result at a start timing of a detection period and asampling result at an end timing thereof. The detection period is set soas to include a transition timing of the detection signal therewithin,and the predetermined minimum time constant may be set to the time ofthe detection period. In this case, the time constant of the conductivefilm may be, for example, equal to or more than ten times or hundredtimes the predetermined minimum time constant.

Moreover, for example, the display device with a touch detectionfunction according to the embodiment of the disclosure may furtherinclude a polarizing plate, and the conductive film may be formedintegrally with the polarizing plate. Furthermore, for example, theconductive film is desirably disposed to cover at least an effectivedisplay region in which the liquid crystal display elements performdisplay operation.

In addition, for example, the display device with a touch detectionfunction according to the embodiment of the disclosure may furtherinclude a plurality of drive electrodes arranged side by side to extendin a direction intersecting with the plurality of touch detectionelectrodes, and an electrostatic capacitance may be formed at eachintersection of the plurality of touch detection electrodes and theplurality of drive electrodes. In this case, the conductive film isarranged on, for example, an opposite side of a detection electrodelayer from the drive electrodes, the detection electrode layer includingthe touch detection electrodes, and a distance between the driveelectrodes and the detection electrode layer is desirably larger than adistance between the conductive film and the detection electrode layer.

For example, the display device with a touch detection functionaccording to the embodiment of the disclosure may further include dummyelectrodes which are arranged between the plurality of touch detectionelectrodes and are in electrically floating state. In this case, forexample, a space between the touch detection electrode and the dummyelectrode adjacent to each other is desirably equal to or smaller than50 μm. In addition, for example, in the effective display region, atotal arrangement area of the touch detection electrodes and the dummyelectrodes is desirably 50% of the area of the effective display regionor more.

For example, the conductive film is desirably supplied with a constantvoltage. In addition, the touch detection electrodes may be arrangedside by side with a pitch of 10 mm or less.

For example, the liquid crystal display elements may be configured toinclude a liquid crystal layer and pixel electrodes arranged to face thedrive electrodes with the liquid crystal layer in between. In addition,for example, the liquid crystal display elements may be configured toinclude a liquid crystal layer and pixel electrodes which are arrangedbetween the liquid crystal layer and the drive electrodes or arearranged on a side opposite to the liquid crystal layer with the driveelectrodes in between.

In the display device with a touch detection function and the electronicunit according to the embodiments of the disclosure, the sheetresistance of the conductive film is set to the predetermined resistancevalue or smaller, and the time constant is set to the predeterminedminimum time constant or larger. Therefore, the display device with atouch detection function and the electronic unit capable of reducingdisturbance of display even when ESD is applied may be realized.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, and are intended toprovide further explanation of the technology as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the disclosure, and are incorporated in and constitutea part of this specification. The drawings illustrate embodiments and,together with the specification, serve to explain the principles of thetechnology.

FIG. 1 is a diagram for describing a basic principle of a touchdetection method in a display device with a touch detection functionaccording to an embodiment of the disclosure, and a diagram illustratinga state where a finger is not in contact with or not in proximity to thedisplay device.

FIG. 2 is a diagram for describing the basic principle of the touchdetection method in the display device with a touch detection functionaccording to the embodiment of the disclosure, and a diagramillustrating a state where a finger is in contact with or in proximityto the display device.

FIG. 3 is a diagram for describing the basic principle of the touchdetection method in the display device with a touch detection functionaccording to the embodiment of the disclosure, and a diagramillustrating an example of a waveform of a drive signal and a touchdetection signal.

FIG. 4 is a block diagram illustrating a configuration example of adisplay device with a touch detection function according to theembodiment of the disclosure.

FIG. 5 is a sectional view illustrating a schematic cross-sectionalconfiguration of a display section with a touch detection functionillustrated in FIG. 4.

FIG. 6 is a circuit diagram illustrating a pixel arrangement of thedisplay section with a touch detection function illustrated in FIG. 4.

FIG. 7 is a perspective view illustrating a configuration example ofdrive electrodes and touch detection electrodes of the display sectionwith a touch detection function illustrated in FIG. 4.

FIG. 8 is a plane view illustrating a configuration example of the touchdetection electrodes of the display section with a touch detectionfunction illustrated in FIG. 4.

FIG. 9 is a sectional view illustrating a configuration example of apolarizing plate illustrated in FIG. 5.

FIG. 10 is a timing waveform chart illustrating an operation example oftouch detection operation in the display device with a touch detectionfunction illustrated in FIG. 4.

FIG. 11 is a schematic diagram illustrating an example of a flow ofstatic electricity in the polarizing plate illustrated in FIG. 9.

FIG. 12 is a schematic diagram for describing a time constant of aconductive film illustrated in FIG. 9.

FIG. 13 is a plot illustrating a relationship between the time constantof the conductive film and S/N ratio of the touch detection signal.

FIGS. 14A and 14B are sectional views illustrating a configurationexample of a polarizing plate according to a modification.

FIG. 15 is a plane view and a sectional view illustrating aconfiguration example of a display device with a touch detectionfunction according to another modification.

FIG. 16 is a perspective view illustrating an appearance configurationof an application example 1, out of display devices with a touchdetection function applied with the embodiment.

FIGS. 17A and 17B are perspective views illustrating an appearanceconfiguration of an application example 2.

FIG. 18 is a perspective view illustrating an appearance configurationof an application example 3.

FIG. 19 is a perspective view illustrating an appearance configurationof an application example 4.

FIGS. 20A to 20G are front views, side views, a top view, and a bottomview illustrating an appearance configuration of an application example5.

FIG. 21 is a sectional view illustrating a schematic cross-sectionalconfiguration of a display section with a touch detection functionaccording to a modification of the embodiment.

DETAILED DESCRIPTION

Hereinafter, preferred embodiments of the disclosure will be describedin detail with reference to drawings. Note that the description will begiven in the following order.

-   1. Basic principle of electrostatic capacitance type touch detection-   2. Embodiment-   3. Application examples

1. BASIC PRINCIPLE OF ELECTROSTATIC CAPACITANCE TYPE TOUCH DETECTION

First, a basic principle of touch detection in a display device with atouch detection function according to an embodiment of the disclosurewill be described with reference to FIG. 1 to FIG. 3. The touchdetection method is implemented as an electrostatic capacitance typetouch sensor, and a capacitance element is configured with use of a pairof electrodes (a drive electrode E1 and a touch detection electrode E2)facing each other with a dielectric body D in between as illustrated in(A) of FIG. 1. The configuration is represented as an equivalent circuitillustrated in (B) of FIG. 1. A capacitance element C1 is configured ofthe drive electrode E1, the touch detection electrode E2, and thedielectric body D. One end of the capacitance element C1 is connected toan alternating signal source (a drive signal source) S, and the otherend P is grounded through a resistor R and is connected to a voltagedetector (a touch detection circuit) DET. When an alternatingrectangular wave Sg ((B) of FIG. 3) with a predetermined frequency (forexample, about several kHz to several tens kHz) is applied to the driveelectrode E1 (one end of the capacitance element C1) from thealternating signal source S, an output waveform (a touch detectionsignal Vdet) illustrated in (A) of FIG. 3 appears in the touch detectionelectrode E2 (the other end P of the capacitance element C1). Note thatthe alternating rectangular wave Sg corresponds to a drive signal Vcomdescribed later.

In a state where a finger is not in contact with (or not in proximityto) the display device, as illustrated in FIG. 1, a current I0 accordingto the capacitance value of the capacitance element C1 flows in responseto charge and discharge with respect to the capacitance element C1. Theother end P of the capacitance element C1 at this time has a potentialwaveform like a waveform V0 in (A) of FIG. 3, and the waveform isdetected by the voltage detector DET.

On the other hand, in a state where a finger is in contact with (or inproximity to) the display device, as illustrated in FIG. 2, acapacitance element C2 formed by the finger is added in series with thecapacitance element C1. In this state, currents I1 and I2 flow inresponse to charge and discharge with respect to the capacitanceelements C1 and C2, respectively. The other end P of the capacitanceelement C1 at this time has a potential waveform like a waveform V1 in(A) of FIG. 3, and the waveform is detected by the voltage detector DET.At this time, the potential of the point P is a partial potentialdetermined by values of the currents I1 and I2 flowing through thecapacitance elements C1 and C2. Therefore, the waveform V1 is a smallervalue than that of the waveform V0 in a non-contact state. The voltagedetector DET compares the detected voltage with a predeterminedthreshold voltage Vth to determine the non-contact state when thedetected voltage is equal to or larger than the threshold voltage, andto determine a contact state when the detected voltage is smaller thanthe threshold voltage. In such a way, touch detection is achievable.

2. EMBODIMENT CONFIGURATION EXAMPLE General Configuration Example

FIG. 4 illustrates a configuration example of a display device with atouch detection function 1 according to an embodiment of the disclosure.The display device with a touch detection function uses a liquid crystaldisplay element as a display element, and is of a so-called in-cell typein which a liquid crystal display section configured by the liquidcrystal display element, and an electrostatic capacitance type touchdetection section are integrated.

The display device with a touch detection function 1 includes a controlsection 11, a gate driver 12, a source driver 13, a drive electrodedriver 14, a display section with a touch detection function 10, and atouch detection circuit 40.

The control section 11 is a circuit supplying a control signal to eachof the gate driver 12, the source driver 13, the drive electrode driver14, and the touch detection circuit 40 based on a picture signal Vdispsupplied from outside, and controlling these parts to operate insynchronization with one another.

The gate driver 12 has a function to sequentially select one horizontalline which is a target of display drive of the display section with atouch detection function 10, based on the control signal supplied fromthe control section 11. Specifically, as described later, the gatedriver 12 applies a scan signal Vscan to a gate of a TFT element Tr of apixel Pix through a scan signal line GCL to sequentially select, as atarget of display drive, one row (one horizontal line) in the pixels Pixformed in a matrix in a liquid crystal display section 20 of the displaysection with a touch detection function 10.

The source driver 13 is a circuit supplying a pixel signal Vpix to eachpixel Pix (described later) in the display section with a touchdetection function 10 based on the control signal supplied from thecontrol section 11. Specifically, the source driver 13 supplies thepixel signal Vpix to each pixel Pix configuring one horizontal linesequentially selected by the gate driver 12 through a pixel signal lineSGL as described later. Then, in the pixels Pix, display for thehorizontal line is performed in response to the supplied pixel signalVpix.

The drive electrode driver 14 is a circuit supplying the drive signalVcom to drive electrodes COML (described later) of the display sectionwith a touch detection function 10 based on the control signal suppliedfrom the control section 11. Specifically, the drive electrode driver 14sequentially applies the drive signal Vcom to the drive electrodes COMLin a time-divisional manner. Then, a touch detection section 30 outputsa touch detection signal Vdet based on the drive signal Vcom from aplurality of touch detection electrodes TDL (described later), andsupplies the signal to the touch detection circuit 40.

The display section with a touch detection function 10 is a displaysection incorporating a touch detection function. The display sectionwith a touch detection function 10 includes the liquid crystal displaysection 20 and the touch detection section 30. As described later, theliquid crystal display section 20 is a section performing sequentialscan on one horizontal line basis to perform display according to thescan signal Vscan supplied from the gate driver 12. The touch detectionsection 30 operates based on the above-described basic principle of theelectrostatic capacitance type touch detection, and outputs the touchdetection signal Vdet. As described later, the touch detection section30 performs sequential scan according to the drive signal Vcom suppliedfrom the drive electrode driver 14 to perform touch detection.

The touch detection circuit 40 is a circuit detecting the presence oftouch events with respect to the touch detection section 30 based on thecontrol signal supplied from the control section 11 and the touchdetection signal Vdet supplied from the touch detection section 30 ofthe display section with a touch detection function 10, and when thetouch event is detected, the touch detection circuit 40 determines thecoordinate and the like in a touch detection region. The touch detectioncircuit 40 includes an analog LPF (low pass filter) section 42, an A/Dconversion section 43, a signal processing section 44, a coordinateextracting section 45, and a detection timing control section 46. Theanalog LPF section 42 is a low-pass analog filter which removeshigh-frequency component (noise component) contained in the touchdetection signal Vdet supplied from the touch detection section 30 toextract touch component, and outputs each of the touch component. Aresistor R for applying a direct-current potential (0V) is connectedbetween each input terminal of the analog LPF section 42 and the ground.Incidentally, by providing a switch, for example, instead of theresistor R and turning the switch on at a predetermined time, thedirect-current potential (0V) may be provided. The A/D conversionsection 43 is a circuit converting each analog signal output from theanalog LPF section 42 into a digital signal by sampling at timings insynchronization with the drive signal Vcom. The signal processingsection 44 is a logic circuit detecting the presence of touch eventswith respect to the touch detection section 30 based on the outputsignal of the A/D conversion section 43. The coordinate extractingsection 45 is a logic circuit determining a touch panel coordinate whenthe touch event is detected by the signal processing section 44. Thedetection timing control section 46 controls these circuits to operatein synchronization with one another.

(Display Section with Touch Detection Function 10)

Next, the configuration example of the display section with a touchdetection function 10 will be described in detail.

FIG. 5 illustrates an example of a cross-sectional configuration of arelevant part of the display section with a touch detection function 10.The display section with a touch detection function 10 has a pixelsubstrate 2, a facing substrate 3 disposed to face the pixel substrate2, and a liquid crystal layer 6 inserted between the pixel substrate 2and the facing substrate 3.

The pixel substrate 2 includes a TFT substrate 21 as a circuit substrateand a plurality of pixel electrodes 22 arranged in a matrix on the TFTsubstrate 21. In the TFT substrate 21, although not illustrated, thinfilm transistors (TFTs) for each pixels and wirings such as the pixelsignal line SGL for supplying the pixel signal Vpix to each of the pixelelectrodes 22 and the scan signal line GCL for driving each of the TFTsare formed.

The facing substrate 3 includes a glass substrate 31, a color filter 32formed on a surface of the glass substrate 31, and a plurality of driveelectrodes COML formed on the color filter 32. The color filter 32 isconfigured by, for example, cyclically arranging three color filterlayers of red (R), green (G), and blue (B), and a set of three colors ofR, G, and B corresponds to each display pixel. The drive electrodes COMLfunction as common drive electrodes for the liquid crystal displaysection 20, and also function as drive electrodes for the touchdetection section 30. Note that in this example, although the driveelectrodes COML are shared for display and for touch detection, thedrive electrodes for display and for touch detection may be separatelyprovided. In addition, for example, instead of the drive electrodesCOML, the scan signal line GCL or the pixel signal line SGL may beshared as drive electrodes for the touch detection section 30. In thesecases, when the scan signal line GCL or the pixel signal line SGL ismade of a low resistance material such as Mo and Al, a low resistancedrive electrode is achievable. The drive electrodes COML are connectedto the TFT substrate 21 through an contact conductive cylinder (notillustrated), and the drive signal Vcom with the alternating rectangularwaveform is applied from the TFT substrate 21 to the drive electrodesCOML through the contact conductive cylinder. On the other surface ofthe glass substrate 31, the touch detection electrodes TDL as detectionelectrodes of the touch detection section 30 are formed. Each of thetouch detection electrodes TDL is made of ITO (indium tin oxide), IZO,SnO, an organic conductive film, and the like, and has translucency.Note that each of the touch detection electrodes TDL may have, forexample, an aperture at a portion corresponding to a pixel of colorlight with low transmittance in the electrode (a pixel of blue (B) in acase of ITO). Further, a polarizing plate 35 is disposed on the touchdetection electrodes TDL. Incidentally, on the polarizing plate 35, acover window configured of glass, film, plastic or the like may bearranged.

The liquid crystal layer 6 modulates light passing therethroughaccording to a state of electric field, and liquid crystal of variousmodes such as TN (twisted nematic), VA (vertical alignment), and ECB(electrically controlled birefringence) is used.

Incidentally, alignment films are disposed between the liquid crystallayer 6 and the pixel substrate 2, and between the liquid crystal layer6 and the facing substrate 3. In addition, an incident-side polarizingplate is disposed on a bottom surface side of the pixel substrate 2,which is not illustrated in the figure.

FIG. 6 illustrates a configuration example of a pixel configuration inthe liquid crystal display section 20. The liquid crystal displaysection 20 has the plurality of pixels Pix arranged in a matrix. Each ofthe pixels Pix has a TFT element Tr and a liquid crystal element LC. TheTFT element Tr is configured of a thin film transistor, and in thisexample, the TFT element Tr is configured of an n-channel MOS (metaloxide semiconductor) TFT. A source of the TFT element Tr is connected tothe pixel signal line SGL, a gate thereof is connected to the scansignal line GCL, and a drain thereof is connected to one end of theliquid crystal element LC. One end of the liquid crystal element LC isconnected to the drain of the TFT element Tr, and the other end thereofis connected to the drive electrode COML.

Each of the pixels Pix is connected mutually, through the scan signalline GCL, to the other pixels Pix which are in the same row of theliquid crystal display section 20. The scan signal line GCL is connectedto the gate driver 12, and the scan signal Vscan is supplied from thegate driver 12. In addition, each of the pixels Pix is connectedmutually, through the pixel signal line SGL, to the other pixels Pixwhich are in the same column of the liquid crystal display section 20.The pixel signal line SGL is connected to the source driver 13, and thepixel signal Vpix is supplied from the source driver 13.

Moreover, each of the pixels Pix is connected mutually, through thedrive electrode COML, to the other pixels Pix which are in the same rowof the liquid crystal display section 20. The drive electrodes COML areconnected to the drive electrode driver 14, and the drive signal Vcom issupplied from the drive electrode driver 14.

With this configuration, in the liquid crystal display section 20, thegate driver 12 drives the scan signal line GCL to performline-sequential scanning in a time-divisional manner so that onehorizontal line is sequentially selected. Then, the source driver 13supplies the pixel signal Vpix to the pixels Pix in the selectedhorizontal line to perform display on one horizontal line basis.

FIG. 7 is a perspective view illustrating a configuration example of thetouch detection section 30. The touch detection section 30 is configuredof the drive electrodes COML and the touch detection electrodes TDLarranged in the facing substrate 3. Each of the drive electrodes COML isconfigured of a stripe-shaped electrode pattern extending in a lateraldirection of the figure. When touch detection operation is performed,the drive signal Vcom is sequentially supplied to each of the electrodepatterns by the drive electrode driver 14, and sequential scan drive isperformed in a time-divisional manner. Each of the touch detectionelectrodes TDL is configured of an electrode pattern extending in adirection orthogonal to an extending direction of the electrode patternof each of the drive electrodes COML. As described later, dummyelectrodes 37 (not illustrated) are arranged between the touch detectionelectrodes TDL. The electrode pattern of each of the touch detectionelectrodes TDL is connected to the touch detection circuit 40. Theelectrode patterns of the drive electrode COML and the electrodepatterns of the touch detection electrodes TDL intersecting with eachother form an electrostatic capacitance at each intersection.

With this configuration, in the touch detection section 30, the driveelectrode driver 14 applies the drive signal Vcom to the driveelectrodes COML to output the touch detection signal Vdet from the touchdetection electrodes TDL, and therefore touch detection is performed.The drive electrodes COML correspond to the drive electrode E1 in thebasic principle of the touch detection illustrated in FIG. 1 to FIG. 3,the touch detection electrodes TDL correspond to the touch detectionelectrode E2, and the touch detection section 30 detects touch events inaccordance with the basic principle. As illustrated in FIG. 7, theelectrode patterns intersecting with each other configure anelectrostatic capacitance type touch sensor in a matrix. Therefore, scanis performed over the entire touch detection surface of the touchdetection section 30 so that a contact position or a proximal positionof the external proximity object is also detectable.

FIG. 8 illustrates a configuration example of the touch detectionelectrodes TDL. The touch detection electrodes TDL are arranged side byside with, for example, a pitch of 5 mm in an effective display regionS. The dummy electrodes 37 are arranged between the touch detectionelectrodes TDL, and the dummy electrodes 38 are arranged at the outerside of each of the touch detection electrodes TDL which are arranged atboth sides of the effective display region S. The dummy electrodes 37and 38 allow the touch detection electrodes TDL to be hardly viewed fromthe outside, and are in an electrically floating state. The polarizingplate 35 is disposed in a region wider than the effective display regionS. In other words, a conductive layer 52 (described later) formed in thepolarizing plate 35 is disposed to cover the effective display region S.Note that eight touch detection electrodes TDL are illustrated in FIG.8, however, the number of the touch detection electrodes TDL in theeffective display region S is not limited thereto, and may be, forexample, nine or more, or seven or less. In addition, in FIG. 8,although the touch detection electrodes TDL and the dummy electrodes 37are formed in a region in which the conductive layer 52 (the polarizingplate 35) is disposed, this is not limitative. The touch detectionelectrodes TDL and the dummy electrodes 37 may be formed outside of theregion in which the conductive layer 52 is disposed.

FIG. 9 illustrates a configuration example of the polarizing plate 35.The polarizing plate 35 has a polarizing layer 54 and the conductivelayer 52. The polarizing layer 54 is a layer having a polarizingfunction. A cover layer 55 is formed on a surface of the polarizinglayer 54, and a hard coat layer 56 is formed on the cover layer 55. Acover layer 53 is formed on a surface of the polarizing layer 54opposite to the surface formed with the cover layer 55, and theconductive layer 52 is formed on the cover layer 53. The conductivelayer 52 is a layer with translucency and conductivity, and is made ofITO, IZO, SnO, an organic conductive film, and the like. As describedlater, the conductive layer 52 is provided for ESD protection. Theconductive layer 52 suppresses disturbance of display due to staticelectricity which is applied from the outside and is then transmitted tothe liquid crystal layer, and suppresses degradation in touch detectionsensitivity to minimum. On the conductive layer 52, an adhesion layer 51is provided to bond the conductive layer 52 with the glass substrate 31provided with the touch detection electrodes TDL and the dummyelectrodes 37 and 38. As illustrated in FIG. 9, a distance d1 betweenthe conductive layer 52 and the touch detection electrodes TDL is set tobe smaller than a distance d2 between the touch detection electrodes TDLand the drive electrodes COML.

Here, the liquid crystal element LC corresponds to a specific example of“a liquid crystal display element” of the disclosure. The conductivelayer 52 corresponds to a specific example of “a conductive film” of thedisclosure.

(Operations and Functions)

Subsequently, operations and functions of the display device with atouch detection function 1 of the embodiment will be described.

(General Operation Outline)

The control section 11 supplies the control signal to each of the gatedriver 12, the source driver 13, the drive electrode driver 14, and thetouch detection circuit 40 based on the picture signal Vdisp suppliedfrom the outside, and controls these parts to operate in synchronizationwith one another. The gate driver 12 supplies the scan signal Vscan tothe liquid crystal display section 20 to sequentially select onehorizontal line to be driven for display. The source driver 13 suppliesthe pixel signal Vpix to each pixel Pix configuring the horizontal lineselected by the gate driver 12. The drive electrode driver 14sequentially applies the drive signal Vcom to the drive electrodes COML.The display section with a touch detection function 10 performs displayoperation, and performs the touch detection operation based on the drivesignal Vcom to output the touch detection signal Vdet from the touchdetection electrodes TDL. The analog LPF section 42 removeshigh-frequency component from the touch detection signal Vdet to outputthe resultant signal. The A/D conversion section 43 converts an analogsignal output from the analog LPF section 42 into a digital signal attimings in synchronization with the drive signal Vcom. The signalprocessing section 44 detects the presence of touch events with respectto the touch detection section 30 based on the output signal from theA/D conversion section 43. The coordinate extracting section 45determines a touch panel coordinate in response to touch detection ofthe signal processing section 44. The detection timing control section46 controls the analog LPF section 42, the A/D conversion section 43,the signal processing section 44, and the coordinate extracting section45 to operate in synchronization with one another.

FIG. 10 illustrates an operation example of the touch detectionoperation, where (A) illustrates a waveform of the drive signal Vcom,and (B) illustrates a waveform of the touch detection signal Vdet. Thedrive electrode driver 14 sequentially applies the drive signal Vcomwith the alternating rectangular waveform illustrated in (A) of FIG. 10to the drive electrodes COML. The drive signal Vcom is transmitted tothe touch detection electrodes TDL through the electrostaticcapacitance, causing an induced current to flow. Then, the touchdetection signal Vdet is changed ((B) of FIG. 10). The A/D conversionsection 43 samples, in a touch detection period Pdet, the output signalfrom the analog LPF section 42, which has received the touch detectionsignal Vdet, at sampling timings ts1 and ts2 in synchronization with thedrive signal Vcom to perform A/D conversion ((B) of FIG. 10). Thesampling timing ts1 corresponds to a start timing of the touch detectionperiod Pdet, and is set immediately before a transition timing of thedrive signal Vcom. In contrast, the sampling timing ts2 corresponds toan end timing of the touch detection period Pdet, and is set immediatelyafter the transition timing of the drive signal Vcom. The signalprocessing section 44 of the touch detection circuit 40 performs touchdetection based on a difference between an A/D conversion result at thesampling timing ts1 and an A/D conversion result at the sampling timingts2. Here, the touch detection period Pdet corresponds to a specificexample of “a detection period” of the disclosure.

Next, the conductive layer 52 will be described. The conductive layer 52is provided for ESD protection in manufacturing the display device witha touch detection function 1 and in its use. In manufacturing,generally, for example, when a cover film is removed from a polarizingplate before adhesion of the polarizing plate, when a cover glass (acover film, or a cover plastic) is adhered to a panel with a transparentadhesive agent, or when a human finger touches a touch detection surface(a surface of the hard coat layer 56) at the time of examination, thepolarizing plate is possibly charged. In addition, in use of the displaydevice with a touch detection function 1, when a charged finger of auser touches the touch detection surface, the polarizing plate ispossibly charged. The conductive layer 52 functions to release thestatic electricity. In the following, functions of the conductive layer52 and electric characteristics for achieving such functions will bedescribed.

FIG. 11 schematically illustrates a flow of static electricity when thestatic electricity is applied. In the display device with a touchdetection function 1, for example, static electricity SE applied to thesurface (the hard coat layer 56) of the polarizing plate 35 is fisttransmitted to the conductive layer 52 through the cover layer 55, thepolarizing layer 54, and the cover layer 53. Then, the staticelectricity SE is transmitted through the conductive layer 52 and thedummy electrodes 37 to the touch detection electrodes TDL arrangedtherearound. After that, the static electricity SE transmitted to thetouch detection electrodes TDL is allowed to be released to a powersource of the display device with a touch detection function or GNDthrough a resistor R (FIG. 4) provided at an input of the touchdetection circuit 40 or an ESD protection circuit (not illustrated)provided in the input section thereof. In other words, in a case wherethe conductive layer 52 is not provided, the static electricity ischarged to the polarizing plate itself, for example, and the electricfield caused by the static electricity may disturb the alignment ofliquid crystal molecules of the liquid crystal layer 6, and may disturbdisplay. However, by providing the conductive layer 52, the staticelectricity is easily released, and the possibility of the disturbanceof display may be reduced. As illustrated in FIG. 8, the conductivelayer 52 is disposed to cover the effective display region S so that thestatic electricity is easily released and disturbance of display isreduced over the entire surface of the effective display region S.

Incidentally, the conductive layer 52 may be disposed to cover a wideregion including the effective display region S. For example, bydisposing the conductive layer 52 to cover a region of circuits arrangedon the pixel substrate 2, breakdown of the circuits may be preventedwhen the static electricity is applied in manufacturing, and malfunctionof the circuits may be reduced when the static electricity is applied inits use.

Each space between the touch electrode TDL and the dummy electrodes 37or 38 adjacent to each other is desirably as narrow as possible in orderto easily release the static electricity, and for example, is desirablyset to 50 μm or less. Moreover, desirably, the touch detectionelectrodes TDL and the dummy electrodes 37 and 38 are arranged so as tohave the total arrangement area as wide as possible in the effectivedisplay region S in order to easily release the static electricity. Forexample, the total arrangement area is desirably 50% of the area of theeffective display region S or more.

It is desirable to make the conductive layer 52 have sufficiently lowresistance in order to easily release the applied static electricity SEto the touch detection electrodes TDL arranged therearound. In otherwords, the resistance of the conductive layer 52 has an upper limit fromthe viewpoint of the ESD protection. Generally, it is known that, toeffectively release the static electricity, the sheet resistance valueof the conductive layer 52 is desirably equal to or lower than 1*10¹²Ω/sq, and is preferably equal to or lower than 1*10¹¹ Ω/sq.

On the other hand, if the resistance of the conductive layer 52 isexcessively low, the touch detection sensitivity may be lowered. Asillustrated in FIG. 7, the display device with a touch detectionfunction 1 detects touch events with use of a change of theelectrostatic capacitance between the drive electrodes COML and thetouch detection electrodes TDL caused by the external proximity object.Therefore, if the resistance of the conductive layer 52 arranged betweenthe touch detection electrodes TDL and the external proximity object isexcessively low, the conductive layer 52 functions as a shield, and theelectrostatic capacitance hardly changes in response to the externalproximity object. In other words, in the touch detection signal Vdet,the touch component indicating the presence of the touch events isattenuated by the shield, the S/N ratio is lowered, and the touchdetection sensitivity is accordingly lowered. As described above, theresistance of the conductive layer 52 has a lower limit from theviewpoint of the touch detection sensitivity.

In other words, the resistance of the conductive layer 52 need to be setto a value in a range between an upper limit defined from the viewpointof the ESD protection and a lower limit defined from the viewpoint ofthe touch detection sensitivity.

Next, the lower limit of the resistance of the conductive layer 52 willbe described in detail.

FIG. 12 schematically illustrates the resistance of the conductive layer52 and a capacitance between the conductive layer 52 and the driveelectrode COML. To prevent the touch component of the touch detectionsignal Vdet from being attenuated by the conductive layer 52 (toincrease the S/N ratio), for example, as illustrated in FIG. 10, thevoltage of the conductive layer 52 needs to show a sufficiently smallchange when the touch detection signal Vdet changes according to thetransition of the drive signal Vcom in the touch detection period Pdet.The voltage of the conductive layer 52 changes depending on a timeconstant τ (=R52·C52) of the conductive layer 52. Accordingly, toincrease the S/N ratio, the time constant τ of the conductive layer 52needs to be larger than a time tdet corresponding to the touch detectionperiod Pdet.

FIG. 13 illustrates a relationship between the S/N ratio and the timeconstant τ of the conductive layer 52. The horizontal axis indicates thetime constant τ of the conductive layer 52 using the time tdet as aunit. The vertical axis indicates the S/N ratio (relative value) whenthe S/N ratio at the time of the time constant τ being infinite(corresponding to a case where the conductive layer 52 is not provided)is defined as 100. Note that in this study, it is assumed that noise isnot affected by the conductive layer 52, and is constant.

As illustrated in FIG. 13, when the time constant τ is small, the S/Nratio becomes small. This is because, as described above, the conductivelayer 52 functions like a shield due to the small time constant τ, andthe touch component is accordingly attenuated. On the other hand, whenthe time constant τ becomes large, the influence of the conductive layer52 is reduced and the S/N ratio is accordingly increased.

Although a necessary S/N ratio depends on use of the display device witha touch detection function 1, as illustrated in FIG. 13, for example,the time constant τ is desirably at least larger than the time tdet. Atthis time, the S/N ratio (relative value) is equal to or larger than 37.Moreover, the time constant τ is preferably equal to or larger than 10times of the time tdet, and the S/N ratio at this time is equal to orlarger than 90. Furthermore, it is more preferable that the timeconstant τ be equal to or larger than 100 times of the time tdet. Atthis time, the S/N ratio (relative value) is equal to or larger than 99,and the touch detection may be performed while being hardly affected bythe conductive layer 52.

In such a way, the time constant τ of the conductive layer 52 is set tothe above described value or larger so that the S/N ratios correspondingto respective values are obtained and the touch detection sensitivity issecured.

In addition, as illustrated in FIG. 8, the conductive layer 52 isdisposed to cover the effective display region S. Therefore, inwhichever portion within the effective display region S the touch eventsoccur, the influence of the conductive layer 52 on the S/N ratio isconstant, so that the variation of the touch detection sensitivitydepending on the touch position is suppressed to minimum.

[Effects]

As described above, in the embodiment, the conductive layer is providedso that disturbance of display is reduced even in a case where staticelectricity is applied.

Moreover, in the embodiment, the time constant of the conductive layeris set to be larger than the time of the touch detection period so thatlowering of the touch detection sensitivity is suppressed to minimum.

Further, in the embodiment, the conductive layer is provided in thepolarizing plate to achieve integration so that manufacturing process isfacilitated. In addition, the integration allows the distance betweenthe conductive layer and the drive electrodes to be reduced. As aresult, the time constant τ is increased as the capacitance C52 isincreased, and therefore the S/N ratio is improved. Furthermore, whenthe resistor R52 is decreased with increase of the capacitance C52, thestatic electricity is allowed to be easily released.

Moreover, in the embodiment, the conductive layer is disposed to coverthe effective display region. Therefore, the disturbance of display maybe suppressed in the entire effective display region, and variation ofthe touch detection sensitivity depending on touch positions may bereduced.

Furthermore, in the embodiment, the distance d1 between the conductivelayer and the touch detection electrodes is set to be smaller than thedistance d2 between the touch detection electrodes and the driveelectrodes. Therefore, the static electricity is allowed to be easilyreleased. In addition, for example, in a case where the resistance ofthe conductive layer 52 is increased as the static electricity isallowed to be easily released, the lowering of the transmittance of theconductive layer or turbidity may be suppressed.

[Modification 1]

In the above-described embodiment, although the conductive layer 52 isprovided between the adhesion layer 51 and the cover layer 53, this isnot limitative. Alternatively, for example, the conductive layer 52 maybe provided between the cover layer 55 and the hard coat layer 56 asillustrated in FIG. 14A, or the conductive layer 52 is formed byconfiguring an adhesion layer 51C with use of an adhesive agentincluding conductive particles 57 as illustrated in FIG. 14B. Also inthis case, by adjusting size and amount of the conductive particles 57included in the adhesive agent and characteristics of the conductiveparticles 57 such as conductivity, the static electricity may beeffectively released, and the lowering of the touch detectionsensitivity may be suppressed to minimum.

[Modification 2]

In the above-described embodiment, although the applied staticelectricity is released through the touch detection electrodes TDL, thisis not limitative. The other path may be provided for releasing thestatic electricity. FIG. 15 illustrates a configuration example of adisplay device with a touch detection function 1B according to amodification 2, where (A) is a plane view, and (B) is a schematicsectional view in the XV-XV arrow direction of (A) of FIG. 15. Thedisplay device with a touch detection function 1B has a GND line 58. TheGND line 58 is arranged around the polarizing plate 35, is electricallyconnected to the conductive layer 52 of the polarizing plate 35, and isconnected to GND of the display device with a touch detection function1B. Accordingly, in the display device with a touch detection function1B, the applied static electricity may be easily released to GND throughthe conductive layer 52.

In the display device with a touch detection function 1 according to theabove-described embodiment, for example, in a case where a switch isprovided in an input of the touch detection circuit 40 connected withthe touch detection electrodes TDL and the switch is turned on only at adetection timing, the pass for releasing the static electricity issecured when the switch is in on state. However, when the switch is inoff state, the pass is blocked and thus, there is a possibility that thestatic electricity is insufficiently released. Even in this case, in thedisplay device with a touch detection function 1B according to themodification 2, since the GND line 58 is connected to the conductivelayer 52 at all times, the pass for releasing the static electricity issecured at all times, allowing the static electricity to be easilyreleased.

[Other Modifications]

In the above-described embodiment, although the touch detectionelectrodes TDL are arranged side by side with a pitch of 5 mm, this isnot limitative. When the pitch between the touch detection electrodesTDL is wide, from the viewpoint of the ESD protection, as illustrated inFIG. 11, there is a possibility that the static electricity SE becomesdifficult to be released due to long path for releasing the staticelectricity SE to the touch detection electrodes TDL through theconductive layer 52. In addition, from the viewpoint of the touchdetection function, the position resolution of touch detection islowered. Therefore, the pitch between the touch detection electrodes TDLis desirably equal to or smaller than 10 mm.

In the above-described embodiment, although the conductive layer 52 isprovided in the polarizing plate 35, this is not limitative.Alternatively, the conductive layer is configured separately from thepolarizing plate.

In the above-described embodiment, although the dummy electrodes 37 areprovided between the touch detection electrodes TDL, this is notlimitative. Alternatively, the dummy electrodes may not be provided.

3. APPLICATION EXAMPLES

Next, application examples of the display devices with a touch detectionfunction described in the embodiment and the modifications will bedescribed with reference to FIG. 16 to FIG. 20G. The display device witha touch detection function of the above-described embodiment and thelike is applicable to electronic units in any fields, such as atelevision device, a digital camera, a notebook personal computer, aportable terminal device such as a mobile phone, and a video camera. Inother words, the display device with a touch detection function of theabove-described embodiment and the like is applicable to electronicunits in various fields for displaying a picture signal input fromoutside or a picture signal internally generated as an image or apicture.

Application Example 1

FIG. 16 illustrates an appearance of a television device to which thedisplay device with a touch detection function of the above-describedembodiment and the like is applied. The television device has, forexample, a picture display screen section 510 including a front panel511 and a filter glass 512. The picture display screen section 510 isconfigured of the display device with a touch detection functionaccording to the above-described embodiment and the like.

Application Example 2

FIGS. 17A and 17B illustrate an appearance of a digital camera to whichthe display device with a touch detection function of theabove-described embodiment and the like is applied. The digital camerahas, for example, a light emitting section for a flash 521, a displaysection 522, a menu switch 523, and a shutter button 524. The displaysection 522 is configured of the display device with a touch detectionfunction according to the above-described embodiment and the like.

Application Example 3

FIG. 18 illustrates an appearance of a notebook personal computer towhich the display device with a touch detection function of theabove-described embodiment and the like is applied. The notebookpersonal computer has, for example, a main body 531, a keyboard 532 foroperation of inputting characters and the like, and a display section533 for displaying an image. The display section 533 is configured ofthe display device with a touch detection function according to theabove-described embodiment and the like.

Application Example 4

FIG. 19 illustrates an appearance of a video camera to which the displaydevice with a touch detection function of the above-described embodimentand the like is applied. The video camera has, for example, a main body541, a lens 542 for shooting an object provided on the front side faceof the main body 541, a shooting start/stop switch 543, and a displaysection 544. Also, the display section 544 is configured of the displaydevice with a touch detection function according to the above-describedembodiment and the like.

Application Example 5

FIGS. 20A to 20G illustrate an appearance of a mobile phone to which thedisplay device with a touch detection function of the above-describedembodiment and the like is applied. In the mobile phone, for example, atop-side enclosure 710 and a bottom-side enclosure 720 are joined by ajoint section (a hinge section) 730. The mobile phone has a display 740,a sub-display 750, a picture light 760, and a camera 770. The display740 or the sub-display 750 is configured of the display device with atouch detection function according to the above-described embodiment andthe like.

Hereinbefore, although the disclosure has been described with referringto the embodiment, the modifications, and the application examples tothe electronic units, the disclosure is not limited thereto, and variousmodifications may be made.

For example, in the above-described embodiment and the like, the displaydevice with a touch detection function is of a so-called in-cell type inwhich a liquid crystal display section and a touch detection section areintegrated. However, this is not limitative, and alternatively, thedisplay device with a touch detection function may be of a so-calledon-cell type in which a touch detection section is provided on a surfaceof a liquid crystal display section, or may be provided with a touchdetection section externally on a surface of a liquid crystal displaysection.

For example, in the above-described embodiment and the like, the displaysection with a touch detection function 10 is configured by integratingthe touch detection section 30 and the liquid crystal display section 20using a liquid crystal of various modes such as TN, VA, and ECB.Alternatively, the touch detection section may be integrated with aliquid crystal display section using a liquid crystal oflateral-electric-field mode such as FFS (fringe field switching) and IPS(in-plane switching). For example, in a case where a liquid crystal inthe lateral-electric-field mode is used, a display section with a touchdetection function 90 may be configured as illustrated in FIG. 21. FIG.21 illustrates an example of a cross-sectional configuration of arelevant part in the display section with a touch detection function 90,and illustrates a state where a liquid crystal layer 6B is sandwichedbetween a pixel substrate 2B and a facing substrate 3B. Since names,functions, and the like of other parts are the same as in the case ofFIG.5, the description thereof is omitted. In the example, unlike thecase of FIG. 5, the drive electrodes COML commonly used for display andfor touch detection are provided directly on the TFT substrate 21, andconfigure a part of the pixel substrate 2B. The pixel electrodes 22 arearranged above the drive electrodes COML through an insulating layer 23.Note that the configuration is not limited to this example, andalternatively, for example, the pixel electrodes 22 may be provided onthe TFT substrate 21, and the common electrodes COML may be provided onthe pixel electrodes 22 through the insulating layer 23. In these cases,all dielectric bodies including the liquid crystal layer 6B, which arearranged between the drive electrodes COML and the touch detectionelectrodes TDL, contribute to the formation of the capacitance elementC1.

The present application contains subject matter related to thatdisclosed in Japanese Priority Patent Application JP 2010-205573 filedin the Japan Patent Office on Sep. 14, 2010, the entire content of whichis hereby incorporated by reference.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalent thereof.

What is claimed is:
 1. A display device with a touch detection surface,the display device comprising: a first substrate having a plurality ofpixel electrodes; a second substrate having a first surface facing thefirst substrate and a second surface facing away from the firstsubstrate; a plurality of liquid crystal display elements between thefirst substrate and the second substrate; a plurality of detectionelectrodes for touch detection; a conductive layer with no touchdetection; a polarizing layer; and a plurality of drive electrodesintersecting the detection electrodes, an electrostatic capacitancebeing formed at each intersection of the detection electrodes and thedrive electrodes, wherein, the detection electrodes, the conductivelayer, and the polarizing layer are sequentially stacked on a secondsurface side of the second substrate, the conductive layer has a sheetresistance value equal to or smaller than a predetermined resistancevalue at which the conductive layer does not provide an effectiveelectrostatic discharge path therethrough, and has a time constantlarger than a minimum time constant defined by sampling timings, and adistance between the drive electrodes and the detection electrode layeris larger than a distance between the conductive layer and the detectionelectrode layer.
 2. The display device according to claim 1, wherein thepredetermined resistance value is 1012 Ω/sq.
 3. The display deviceaccording to claim 2, further comprising a touch detection circuit thatdetects an external proximity object by sampling a detection signal,wherein: the touch detection circuit detects the external proximityobject based on a difference between a sampling result at a start timingof a detection period and a sampling result at an end timing of thedetection period, the detection period being set to include a transitiontiming of the detection signal therewithin, and a time length of thedetection period is employed as the minimum time constant.
 4. Thedisplay device according to claim 3, wherein the time constant of theconductive layer has a value equal to or more than 10 times the minimumtime constant.
 5. The display device according to claim 3, wherein thetime constant of the conductive layer has a value equal to or more than100 times the minimum time constant.
 6. The display device according toclaim 1, wherein the conductive layer is integratal with the polarizinglayer.
 7. The display device according to claim 1, wherein theconductive layer overlies at least an effective display region in whichthe liquid crystal display elements are allowed to perform the displayoperation.
 8. The display device according to claim 1, furthercomprising a plurality of dummy electrodes which are arranged betweenthe detection electrodes.
 9. The display device according to claim 8,wherein the dummy electrodes are maintained in an electrically floatingstate.
 10. The display device according to claim 8, wherein a distanceof a space between an adjacent detection electrode and dummy electrodeis equal to or smaller than 50 μm.
 11. The display device according toclaim 8, wherein a total arrangement area of the detection electrodesand the dummy electrodes, within an effective display region in whichthe liquid crystal display elements are allowed to perform the displayoperation, is 50% of the area of the effective display region or more.12. The display device according to claim 1, wherein the conductivelayer is connected to a constant voltage source.
 13. The display deviceaccording to claim 1, wherein the detection electrodes are arranged in aside by side relationship with a pitch of 10 mm or less.
 14. The displaydevice according to claim 1, wherein the liquid crystal display elementsinclude a liquid crystal layer and pixel electrodes, the pixelelectrodes (a) being between the liquid crystal layer and the driveelectrode or (b) being arranged on a side of the drive electrodes facingaway from the liquid crystal layer.
 15. The display device according toclaim 1, further comprising a touch detection circuit that detects anexternal proximity object by sampling a detection signal.